While Google originally announced Duo back in March, the video calling app is finally about to be launched worldwide this week. 

A new alternative to apps like FaceTime and Skype, Duo is available for both Android and iOS devices and promises to be fast, easy to set up, reliable and initiative.

One feature we’re particularly big fans of is Knock Knock which allows you to see part of the live video of the caller before you answer.
 

You can pre-register for Duo now on the Play Store.